Pump



April 8, 1930. j- P FERRlS 1,753,562

PUMP

Filed June 20, 1927 5 Sheets-Shea? l /f/J 3,2, l w C) /02 www INVENTOR.

L/Zyhzy E Fam/5..

A TTORNE Y.

April 8, 1930. J, pf FERRls 1,753,562

u V 1 I PUMP Filed June 2o', 1927 5 sheets-sheet 2 v l l i raf/f W////////////////////////////// I INVENTOR.

L/HNE 77E/P515..

BY v.

ATTORNEY.

J. P. FERRIS April 8, 930.

PUMPl Fild June 20, 1927 5 Sheets-Sheet 5 e? A.. 4,. 4. o Il uw @www INVENTOR. L/Z7HN .EPH/5- @www ATTORNEY;

April 8, 1930.

J. P. FERRls 1,753,562

PUMP

Filed June 20, 1927 5 Sheets-Sheet 4 INVENTOR.

A TTORNEY,

April s, 1930. J', R FERRE 1,753,562

PUMP

Filed June 20, 1927 5 Sheets-Sheet 5 L/HNE FEM/5. B Y gif/ani ATTORNEY.

Patented Apr. 8, 1930 UNITED STATES PATENT OFFICE TOEN P. FERRIS, 0F MILWAUKEE, WISCON'SIN, ASSIGNOR T0 THE OILGEAR COMPANY,

0F MILWAUKEE, WISCONSIN, A CORPORATION 0F WISCONSIN I l BUMP Application led `Tune 26,.

This invention relates to variable delivery pumps for use primarily in effecting the hydraulic operation of machine tools and the like. i

5 A One object of the present invention is the inspection and repair, is aforded by virtue of the ease with which the unit may be removed from within the frame.

Another object is the provision of a liquid seal for a gear pump or the like which will prevent the admission of air thereto when placed outside of the supply reservoir.l

' Another object is` the provision of improved means for regulating and controlling the rate and direction of flow in a pump fed` hydraulic circuit. This isl accomplished by combining a distributing valve for controlling the direction of flow with an independently operable displacement regulating means for controlling the rate of flow.

Another. object is the provision of means for regulating pump displacement which will permit manual adjustment to determine the initial rate of pump delivery and operable to effect. a predetermined increase in pump de livery and a return to the rate initially set. Other objects and advantages will appear from the following description of an illustrative embodiment of the present invention.

In the drawings:

Figure 1 is a front elevation of a pump mechanism constructed in accordance with the present invention.I

Fig. 2 is a vertical sectional view, taken substantially along the line 2 2 of Figure 1, and illustrating its application to the frame of a machine to be driven.

Fig. 3 is a vertical sectional view, taken along the line 3 3 ofx'Figure 2.

Fig. 4 is a vertical sectional view, taken 1927. serial No. 199,925.

in the same plane but looking in the opposite direction. E

Fig. 5 is a fragmentary rear elevation. Fig. 6 is a horizontal sectional view. Figs. 7, 8, 9 and 10 are sectional views of the valve shown in Figure 3, showing the same in various characteristic positions.

The pump selected for illustration includes a heavy plate 10, constituting a support for the various operating and Control parts of the pump, and adapted for direct application to the main frame 11 of the machine to be driven.

In Figure 2 the plate 10 is shown removably secured over an opening 12 in the frame 11 with the operating parts of the pump.

housed within the frame. The operating parts are carried by a main casting 13 removably secured to and against the inner face of the plate 10 by appropriate means such as bolts 14. A drive shaft 15, extending throughalined openings 16 and 17 in the plate 10 and casting 13, is journaled in appropriate antifriction bearings 18 and 19 and carries'a pulley 20 or other suitable driving means upon the exposed end thereof. Bearing 18 is retained in a chamber 21 formed in the plate 10 and closed by a removable cover plate 22', which cooperates with suitable packing 23 and packing nut 24 to seal the chamber 21 against leakage. The other bearing 19 -is seated within an open chamber 25 formed in the rear face of the casting 13.

- STW() intermeshing gears 26`ad 27 are snuglyllousd Within a chamber 28 formed in the front face of the casting 13 and closed by the rear face of the plate 10. These gears cooperate with each other and with the chamber to provide a gear pump of a well known type. Gear 26 is keyed to and driven bythe shaft 15 while gear 27 rotates upon a stud 29 rigidly anchored `in the casting 13.y The gear pump drawsliquid from an appropriate sump 30 provided within the machine frame /11 through a pipe 31, which communicates with the chamber 28'th'rough a passage 32 in the .casting 13 at one side of the gears, and discharges .this liquid through a port 33 formed in the rear face of the plate 10 and disposed at the other Side of the gears. Port 33 communicates with an inclined passage 34 formed in the plate 10 and leading to an appropriate control valve preferably such as will be described hereinafter.

A chamber formed in the casting 13 above the gear pump and closed by the rear face of plate l0, communicates with a groove 36 which completely surrounds the gear pump -let 40, which communicates with` a pipe 41 leading to the sump 30. l

The shaft 15 also drives a variable displacementy pump of a well known type. That shown in Figures 2 and 5 is similar in many respects to the pumps fully described 'in my.

issued Patent.No. 1,619,200, and in my copending application Serial No. 87,791, filed February 12, 1926.- It comprises a substantially circular driver 42 keyed to the inner end of the shaft 15 so as to rotate therewith` about a fixed horizontal axis. Within the driver 42 is a cylinder barrel 43 mounted for rotation about a pintle 44, fixed in and projecting from a depending rock arm 45. The

v arm 45 is supported by an integral sleeve 46,

rotatably mounted upon a hollow cylindrical stud 47, projecting horizontally from and firmly anchored in the upper portion of the casting 13. The cylinder barrel 43 is formed with a series of radial boresl48 each having a piston 49 reciprcable therein. Each piston is provided with a cross-head 50 which reacts through a roller bearing 51 against-one of a series of tangential reaction faces 52 on the driver 42. Each bore 48 is formed with a port 53 arranged to communicate alternately with gashes 54l and55, formed in the opposite sides of the pintle 44.- A passage 56k communicating-with 'gash 54 leads throng `the pintle to a passage 57 in the arm 45, and

a similar passage 58 communicates with gash and a second passage 59 in the arm 45. Passages 57 and 59. communicate withpipes 60 and 61, respectively, through separate tubes one of which 'is shown at 62 in Figure 5, in the mannerdescribed in the above entitled application. Tubes 62 form a flexible hydraulic connection between the rock arm 45 and a clamp element 63 firmly fixed upon the end of the stud 47 in a manner fully described in said application. The shaft 15. is driven at constant speed. When the arm 45 is in such position that the pintle '44 is concentric with the shaftrl pump displacement The 'level of the liquidin is zero and there is no flow in pipes 60 and 61, and when thel arm is shifted toward the right (Fig. 5) so las to effect a laterally offset relation between the 'pintle and shaft the pump delivers liquid through' passages 56 and 57 and pi e 60 at a rate determined by the degree of t 1e offset relation and'receives liquid through pipe 61 and passages 59 and 58 at a corresponding rate. s

\ The clamp element 63 in this'instance is extended to provide a rigid locating arm 64 disposed besidecthe rock arm 45. The locating arm lcarries a roller 65 which cooperates with a rotary'cam 66 on the rock arm 45 to regulate the position thereof and thereby regulate pump displacement. The cam 66 is journaled in the rock arm 45 and is operatedv and controlled through appropriate gearing such Vvas that described in my issued patent hereinabove mentioned. The gearing herein shown comprises a gear 67 connected to the cam 66 through a shaft 68, to which. both are secured, an idler=gear 69, carried by the rock arm, which meshes with gear 67 and with a gear 70, keyed to a rotary stem 71. The stem extends through the gear 70, hol'- low stud 47, casting 13 and plate 10, and at its exposed end carries an appropriate 'hand control lever 72 keyed thereto. An appropri ate clamp nut 73 retains the gear 70 upon the end of the stem and cooperates with a collar 74 on the stem to retain the same against end play. The base of the hand lever 72 is preferably shaped to provide an indicating dial 76 having a suitable pointer 77 forcooperation with a graduated scale 7 8 formed .on the front face of the plate 10, l A second clamp nut 79 threaded on the forward end Y of the stem 71 serves to clamp the dial 76 againstthe f ace of the plate-10 to thereby releasablysecure the same, and consequently the stem, in any position of rotative adjust;l

ment. with an appropriate handle 80. Upon releasing thel nut 79 the hand lever 72 may be swungthe cam 66 which reacts against the'roller 65 toshift the. rock arm 45 and consequentlyv the pintle 44 toward or from concentric relation with the drive shaft 15. In this mannerv the displacement' ofthe pump may be varied i at will and thereafter retained in any position ofadjustment by tighteningfthe nut 79. Any suitable means. such as a spring loaded tension vholt 81, connecting the fixed locating The nut79 preferably equipped arm 64 with the rock arm 45, may be employed to normally retain the cam 66 against the roller 6 5. y

Additional displacement regulating means is provided in the pump shown by which the displacement thereof may be temporarily increased over that which may have been determined by the setting of the adjustment just described. This vadditional regulating 83, formed as an integral part of the fixed locating arm 64. A contact element 84, carried by the piston 82, is disposed to thrust against a pin 85, fixed in the rock arm 45, to thereby force the arm 45 toward the right (Fig. 5) when the piston 82 is advanced. A passage 86'in the arm 64 effects communication between the cylinder 83 and a. pipe 87 through which fluid pressure is supplied under the control of mechanism to be hereinafter described. The extent of advance of the piston 82 is regulated and controlled by appropriate means such as a tail rod 88, fixed to the piston and projecting outwardly through the end of the cylinder 83, and 'carrying a suitable nut 89 adj ustably fixed thereon. The nut 89 serves as an adjustable stop which cooperates with the face 90 of the arm 64 to'limit the advance of the piston 82. `It will thus be understood that whenever fluid pressure is applied to pipe 87, the piston 82 is advanced to a position predetermined by the setting of the nut 89, the arm 45 is forced to the right to a corresponding predetermined position, and pump displacement is increased accordlngly.

In the pump mechanism shown vthe discharge side of the constant displacement gear pump is permanently connected with the`intake side of the variable displacement pump, and provision is made for maintaining the pressure within those connections substantially constant. In this instance the passage 34, hereinabove mentioned, which receives the discharge from the gear pump, communicates through a port 91, in the rear face of the plate 10, with the lower end of a vertical groove 92, formed in the front face ofthe casting 13 and closed by the coacting face of the plate 10. Groove 92 communicates at its upper end with a horizontal passage 93, which extends rearwardly through the casting 13, and communicates through a pipe 94 with the end chamber 95V of an appropriate low pressure relief valve. Pipe 61, leading to the intake side of the variable displacement pump also communicates with chamber 95. A second chamber 96 formed in the casting 13 communicates with the -chamber 35, hereinbefore described,

through the passage 3 9. A valvel plunger 97, controlling communication between chambers 95 and 96, is yieldably retained in the position shown in Figure 6 'by the pressure of fa springv 98 housed within a bore 99 within the casting 13. Spring 98 is interposed between the plunger 97 and a tension adjusting's'crew 100 threaded in and projegtilig through the plate 10. the' position shown the plunger 97 blocks communication between chambers 95 and 96. The plunger 97 assumes this position when the pump is at rest and when there is no pressure within the chamber 95. The capacity of the gear pump is somewhat greater than the demands upon it, however, so that when the pump mechanism isset in operation pressure builds up in the passages 33 and 34, port y91, groove 92, passage 93, pipe 94, chamber 95, and pipe 61, until the plunger 97 is forced back against the pressure in spring 98 and the excess liquid escapes into and through chamber 96 and passage 39 to the chamber 35. This condition maintains throughout the normal functioning of the pump mechanism so that a predetermined pressure, determined by the tension in spring 98, is maintained throughout the hydraulic connections just mentioned. The excess liquid discharged through the passage 39 into the chamber 35 serves to maintain a body of liquid within this chamber for the purposes hereinabove pointed out.

The hydraulic pressure maintained by the gear pump in the groove 92 may be utilized as a pressure supply source for operating some auxiliary mechanism with which the machine may be equipped. To this end a passage 101 is formed through the plate 10 in such position as to register with the groove 92, when the casting 13 is assembled therewith. An elbow 102 or other appropriate outlet element, attached to the front face of the plate 10, communicates with the passage 101 and provides an appropriate connection for receivin a pipe lead to such auxiliary mechanism. W en no auxiliary mechanism is used the elbow is ordinarily plugged.

The discharge from the variable displacev ment pump is placed under the control of a distributing valve of appropriate type which, in the pump mechanism shown, is made a part of the plate 10. In this instance a horizontal, bore 103 is formed within the lower portion of the plate extending from edge to edge thereof. Thisbore is closed by appropriate end caps 104 and 105 and at opposite ends is enlargedto form chambers 106 and 107. Passage 34, which receives the discharge from the ear pump leads downwardly into end chamer 106. n vannular groove 108, surrounding the bore 103, communicates through a passage 109 in the plate 10, with an elbow 110 l y' i fixed tothe front of the plate and adapted to receive a pipe 111 constitutlng one side of 'a main motor circuit. A, similar gropve'112 communicates with a passage 113 which leads cuit. A similar groove 118 communicates with a drain passage 119 which extends through the plate 10 and discharges rearwardly into the sump beneath the pump mechanism. The forward end of drain passage 119 also communicates with 'an elbow 120, attached to the front of the plate- 10, serving as a convenient pipe connect-ion for carrying off the exhaust liquid from the auxiliary mechanism hereinabove referred to. When no auxiliary mechanism is employed this elbow'120 is plugged. A similar groove 121 communicates through a passage 122 in the plate. to which the pipe 87 (leading to the pump displacement regulating cylinder 83) is connected.

The several grooves 108, 112, 114, 118, and 121 are controlled by a suitable valve plunger 123 mountcd for lengthwise reciprocation within the bore 103. The plunger shown contains a longitudinal passage 124 through Vwhich communication is maintained between the end chambers 106 and 107. A piston head 125 on the plunger controls the groove 108, a similar head 126 controls the grooves 112 and 114, and a similar head 127 /controls the groove 121. An elongated head 128, intermediate the heads 126 and 127, contains ports 129,

Lwhich communicate with the longitudinal passage 124. Head 128 controls the groove 118 and cooperates with an annular chamber 130, surrounding the bore, to make and break communication between the groove 114 and ports 129. The plunger is designed to assume any one of the five positions shown in Figures 3, 7, 8, 9 and 10, and is actuated and c ntrolled through a stem 131, connected to one end thereof, from any appropriate means such as a hand lever 132.

The motor driven by the pump is typified by a conventional cylinder 133, containing a piston 134, connected to a piston rod 135 projecting through one end only of the cylinder. Due to the li uid displaced by the rod, that end of the cylinder containing the rod is of less capacity than the other end, and will be hereinafter designated the small end to distinguish from the other hereinafter termed the large end. It will be noted that pipe 111 communicates with the large end and pipe 117 with the small end of the cylinder.

In operation the drive shaft 15 is rotated at constant speed so that the gear pump, comprising the gears 26 and 27, draws liquid from the sump 30 through pipe 31 and passage 32 and forces the same through passages 33 and 34, port 91, groove 92, passage 93, pipe 94, and chamber 95 to the pi 61 leading to the intake side of the varia le displacement pump. Due to the excess capacity of the gear pump over the demands upon it the valve plunger 97 is forced back against the pressure in spring 98, permitting the excess liquid to escape through chamber 96 and passage 3 9 to the chamber 35. A predetermined pressure determined by the adj ustmentvof screw 100 is thus maintained within the pipe 61 leading to the intake side of the variable displacement pump. This pressure is also transmitted through passage 34 to the end chamber 106 of the control valve, and also through the longitudinal assage 124 to the other end chamber 107. oth end chambers 106 and 107 and the interior of valve plunger 123 are thus maintained flooded with' liquid under pressure. The shaft 15 also drives the driver 42 of the variable dis lacement pump at a constant rate so that tliis pump, receiving liquid through pipe 61, delivers the same through pipe 60 into the groove 112, at rate depending upon the position of the rock arm 45 and pintle 44.

With the plunger 123 of the control valve in the intermediate position shown in Figure 3, groove 112 is in open communication 'with end chamber 106, so that liquid discharged from the variable displacement pump passes through chamber 106, ,passage 34, port 91, groove 92, passage 93, pipe 94, and chamber 95 and returns to the variable displacement pump through pipe 61. This pump is thus y-passed, both sides thereof being exposed to the pressure maintained by the gear pump in chamber 95. With valve plunger 123 in this position groove 108 is also open to the pressure in end chamber 106 so that pipe 111, leading to the large end of the motor cylinder 133, is exposed to this pressure;but groove 114, communicating with the small end of the cylinder through pipe 117, opens into the dead space confined between the heads 126 and 130 so that there can be no flow through pipe 117 and the piston 134 is thus effectively blocked. It will also be noted that in this positioxp of the valve plunger 123, groove 121 is open to the drain groove 118 so that pipe 87, leading to the stroke change cylinder 83, is open to exhaust and the rock arm 45 and pintle 44 assumes the position determined by the cam 66. As indicated in Figure 1 the control lever 72 for the cam 66 is in an intermediate position so that the variable displacement pump is operating at about one half of maximum capacity.

When by adjusting the hand lever 132 the valve' plunger 123 is shifted into the position shown in Figure'9 groove 121 is still open to groove 118 and pump displacement remains unchanged. In this position of plunger 123 groove 112 communicates with groove 114 so that the liquid discharged from the variable displacement pump, throu h'pipe 60, passes through these grooves an pipe 117'to the small end of the motor cylinder 133 so that the piston 134 is then driven toward the right at a rate dependent upon the setting of the cam 66. As the piston travels toward the right the liquid escapes fromthe large Aend of the cylin er through pipe 111, groove 108, end chamber 106, passage 34, etc. into the chamber 95 from whence it escapes past the plunger 97 or through the pipe 61 back to the variable displacement pump. To increase the rate of travel of the piston 134 toward theright the valve plun er 123 is shifted into the position shown in igure 10. In this position groove 112 is still open to groove 114 and groove 108'is still open to end chamber 106 so that the pump-motor vcircuit remains the same. But in this position groove 121 is exposed to the pressure in end chamber 107 so that the pressure is transmitted through pipe 87 to the cylinder 83, the piston 82 advances, and the element 84, engaging the pin .85 forces the rock arm 45 toward the right (Fig. 5) to increase the displacement of the variable displacement pump. This results in a corresponding ,increase in flow in pipes 60 and 117 with a corresponding increase in the rate of travel of the piston 134.

To operate the piston 134 at a relatively slow rate in the opposite direction the valve plunger 123 is shifted into the position shown in Figure 7, in which position groove 108 is closed to chamber 106 and open to groove 11.2, sothat the liquid discharged by the pump through pipe l6'0 is directed through grooves 112 and 108 and pipe 111 to the large end of the cylinder 133. In this position of the plunger 123 groove 114 is closed to groove 112 and open to end chamber 106 through chamber 130, ports 129 and longitudinal passage 124 through the plunger, so that as the piston 134 is driven toward the left by the iow of liquid through pipes 60 and 111, liquid from the small end ofthe cylinder 133 passes through the end chamber 106 to the chamber 95 in the low pressure relief valve and thence through pipe 61 back to the variable displacement pump. Since the two ends of the cylinder 133 are of different capacities the large end consumes more liquid than is dischargedfrom the small end. Due to this deficiency the liquid discharged from the small end of the cylinder to chamber 95 is supplemented by liquid supplied from the gear pump through assage 33 to thereby insure that the varia le displacement pump may be sup lied with liquid as fast as it is discharged t erefrom. It will be noted that in the position of the valve plunger 123 shown in Figure 7 groove 121 is open to drain groove 118 so that the cylinder 83is open to exhaust and the variable displacement pump is discharging at a relatively low. rate determinedby the setting of the cam 66.

To increase the rate of travel of the piston 134 toward the left the plunger 123 is shifted into the position shown in Figure 8, in which position groove 121 is exposed to the pressure in end chamber 107 and the piston'82 (Fig. 5) is again advanced -to increase pump displacement `and thereby increase the rate of How-through pipe 60;to' the groove 112.

Also groove 114 is closed to chamber 130 and open to groove 108 so that als the piston 134 continues its travel toward the left the liquid discharged from the small end thereof, through pipe 117, is directed throu h grooves 114 and 108 to the pipe 111 to there y supplement the liquid supplied from the pump through groove 112 to effect a corresponding further increase in the rate of travel of the piston. When both ends of the cylinder 133 are thus exposed to the delivery side of the pump the piston 134 travels toward the left by reason of the fact that the effective area of the left end face of the piston is reduced by the piston rod connection.

Provision is made in the pump mechanism shown for protecting the circuit against excessive pressures and to this end a high pressure relief valve is provided connected to the delivery pipe 60 leading from the variable displacement pump. A relief valve for this purpose is shown in Figure 6. In this instance this valve comprises .an element 140 normally seated over and closing the end of a priate outlet port 146 through which liquid escaping past the valve element 140 may pass and retuan to the sump 30 below.

Various changes may be made in the embodiment of the invention hereinabove specically described without departing from or sacrificing any of, the advantages of the invention as defined in the appended claims.

I claim 1'. In a device of the character described thecombination of a plate, a variable displacement pump supported thereby, driving means for said pump supported by andeX- tended through said plate, and pump regulating means supported by said plate.

2. In a device of the character described the combination of a plate, a pump supported thereby, 'shafting supported by and extended through said plate for driving said pump, and valve mechanism supportedby Vsaid plate for controlling the liquid discharged by said' pump.

3. In a device of the character described" the combination of a plate, a drive shaftextended through said plate, a variable displacement pump supported by said'l plate and driven by said shaft, a second pump supported by said plateand `driven-by saiglnjsrhaft,l

and means supported by said plate for controlling the discharge from said pumps.

4. In a device of the character described the combination of a plate, a drive shaft extended through said plate, a variable displacement pump supported by said plate and driven by said shaft, pump regulating means supported by said plate, passages in said plate for connection with a hydraulic circuit, and hydraulic connections between said pumfind passages.

5.` a device of the character described the combination of a frame having an opening, a plate attachable to said frame over said opening, a variable displacement pump carried by said plate, pump driving means extended through and carried by said plate, and pump regulating means carried by said plate, said pump and both of said means being combined for projection as a unit through said opening upon application of said plate to said frame.

6. In a device of the character described the combination of a to and supported by said plate, a pump supported by said casting, said plate having means for' connection with a hydraulic circuit, hydraulic connections between said pump and means, and a valve supported by said plate for controlling said connections.

7. In a device of the character described the combination of a variable displacement pump, fluid actuated means for varying pump displacement, valve mechanism for -receiving and directing the flow of liquid discharged by said pump, and fluid connections controlled by said valve mechanism for controlling said displacement varying means.

8. In a device of the character described the combination of a variable displacement pump, fluid actuated means for varying pump displacement, valve mechanism for receiving and irecting the How of liquid discharged by said pump, and means responsive to adjustment of -said valve mechanism for controlling the operation of said displacement varying means.

9. In a device 'of the character described the combination of a variable displacement pump, hydraulically actuated means for varying pump displacement, valve mechanism for. receivin anddirecting the flow of liquid discharge by said pump, a second pump, and means responsive to adjustment of said valve mechanism for controlling communication between said second pump and said displacement varying means.

10. In a device of the character described the combination of a variable displacement ump, a second pump, hydraulic connections tween said pumps, a liquid reservoir below said second pump, a hydraulic connection between said reservoir and second pump, and means providing ay liquid seal for said second pump to prevent the admission of air thereto. 11. In a device of the character described plate, a casting ixed- Supporte tween said reservoir 'and said inlet passage,

and means providing a liquid seal for said housing to prevent. the admission of air' thereto.

12. In a device of the character described the combination of a pump housing having .inlet and outlet passages, liquid impelling means within said housing for inducing a liquid How between said passages, a liquid reservoir, a hydraulic connection between said reservoir and inlet passage, a pressure relief valve, and means providing a liquid seal for said housing to prevent the admission of air thereto, said means including an auxiliary chamber supplied with liquid discharged from said relief valve.

18. In a device of the character described the combination of a pump housing having a shaft receiving opening and inlet and, outlet passages, a drive shaft in said opening, liquid impelling means within said housing for vinducing a liquid How between said passages,

a liquid reservoir, a hydraulic connection between said reservoir and inlet passage, and means providing a liquid seal for said housing to prevent the admission of air thereto, said means including an auxiliary liquid retaining chamber open to said opening to Hood the same.

14. In a device of the character described the combination of a variable .dis lacement pump, a hydraulic circuit fed thereby, means adjustable by the operator for initially determining pump displacement, valve mechanism for controlling communication between said pump and circuit, and means controlled by said valve mechanism for modifying pump displacement.

15. In a device of the character described the combination of a variable displacement pump, means adjustable by the operator for initially determining pump displacement, additional means for modifying pump displacement, and valve means for controlling the operation of said last named means.

` 16. In a device of the character described the combination of a plate, a variable displacement pump supported thereby, means supported by and operable throlgh said plate for initially determining pump splacement, fluid actuated means sup rted by said plate for modiing pump disp acement, and means y said plate for controlling said last named means.

17. In a device of the character described the combination of a support, a variable displacement pump suprorted thereby, a rock arm adjustable on sai support to vary pump displacement, means .adjustable by the operator for initially determining the position of said arm,.uid actuated means for shifting said arm from the position initially set, and adjustable means for accurately limiting the action of said last named means. 4

18. In a device of the character described the combination of a plate, a casting supported thereby, a variable displacement pump supported by said casting, a second pump, cooperating fluid passages in said plate and casting for connecting said pumps, shafting extended through said plate for driving said pumps, means on said plate for connection with a hydraulic circuit, hydraulic connections between said last named means and said variable displacement pump, addition means on said plate for connection with an auxiliary hydraulic circuit, hydraulic connections between said last namedmeans and said second pump, and means operable through said plate for varying the displacement of said iirst named pump.

19. The combination of a variable displacement pump, displacement regulating means,.

a hydraulic circuit, valve mechanism between said pump and circuit adjustable to vary the direction of flow therein, a second pump, and hydraulic connections between said second pump and circuit controlled by said valve mechanism. l

In witness whereof, I hereunto subscribe my name this 15th day of June, 1927.

JOHN P. FERRIS. 

